LYMPHOSIS. 



673 



are to the red. Such has been presumed to be one of their offices, but 

 it will be seen, hereafter, that all the tissues supplied with vessels receive 

 red blood; and hence it is unnecessary to suppose, that the lymphatics 

 execute any venous function. 



Assuming, for the present, that lymph is wholly obtained from 

 materials already deposited in the body ; the next inquiry is, the mode 

 in which its formation and simultaneous absorption are effected. On 

 this topic, we have no arguments to employ in addition to those adduced 

 regarding the function of the chyliferous radicles. In every respect, 

 they are situate identically, and to the history of the latter we must 

 refer for an exposition of the little we know of this part of lymphosis. 



The causes of the progression of the lymph in the vessels are the 

 same as those that 



influence the chyle. Fig. 260. 



In addition, however, 

 to those mentioned 

 under chyliferous ab- 

 sorption, there is one 

 that applies equally 

 to the chyliferous 

 and lymphatic ves- 

 sels : this is the mode 

 in which the thoracic 

 duct enters the sub- 

 clavian vein. It has 

 been already observ- 

 ed that it occurs at 

 the point of junction 

 between the jugular 

 and subclavian, as at 

 D, Fig. 260, where J 

 represents the jugu- 

 lar, and V S the subclavian, in which the blood flows from V towards 

 S, the cardiac extremity. 



Now, it is a physical fact, that when a small tube is inserted per- 

 pendicularly into the lower side of a horizontal conical pipe, in which 

 water is flowing from the narrower to the wider portion; and if the 

 small vertical tube be made to dip into a vessel of water, not only will 

 the water of the larger pipe not descend into the vessel ; but it will 

 draw up the water through the small tube so as to empty the vessel. 1 

 Instead of supposing the canals in Fig. 260, to be veins and the tho- 

 racic duct; let us presume that they are rigid mechanical tubes; and 

 that the extremity of the tube D, which represents the thoracic duct, 

 dips into the vessel B. As the fluid, proceeding from J to S and 

 V to S, is passing from the narrower portions of conical tubes to wider, 

 it follows, that the fluid will be drawn out of the vessel B, simply by 

 traction, or, by what Venturi 2 terms the lateral communication of fluids. 

 This would happen in whatever part of the vessel the tube B D termi- 



1 Sir C. Bell, in Animal Mechanics, p. 41, Library of Useful Knowledge, Lond., 1829. 



2 Sur la Communication Laterale duMouvement dans les Fluides, Paris, 1798. 



VOL. i. 43 



Termination of Thoracic Duct. 



